1. Field of the Invention
The present invention relates to recording and reproducing of image data, and more particularly to recording and reproducing encoded image data.
2. Related Background Art
In a conventional apparatus of this type, image data is divided into blocks each having a plurality of pixels, data of each block is orthogonally transformed, the orthogonally transformed data is quantized and variable-length encoded so as for the orthogonally transformed data of all the plurality of blocks to have a predetermined code amount, and the quantized and encoded data is transmitted or recorded.
In some cases, not only a moving image but also a still image is transmitted or recorded.
In recording a still image, image data of one frame is stored in a memory and repetitively read therefrom to divide it into blocks, orthogonally transform, quantize, encode, transmit, and record it.
The visual characteristics of human eyes find degraded image quality of a still image more easily than a moving image. Therefore, if the same data compression scheme, such as block formation, orthogonal transform, quantization, and encoding, is used both for recording a moving image and for recording a still image, the degraded image quality becomes more conspicuous in a still image mode.
For example, a boundary between blocks may be distorted lowering the quality of images and voices.
Degraded image quality of a still image becomes conspicuous, particularly at an edge portion or at a flat portion. In order to obtain a high quality still image, quantization and variable-length coding may be performed at a lower compression factor of a still image than a moving image.
With this method setting a lower compression factor of a still image than a moving image, however, two series of circuits for processing the still and moving images are required, increasing the whole circuit scale.